The present invention relates generally to the fragmenting of articles made from rubber or synthetic plastic material, and more particularly to the fragmenting of such articles, and in particular of automobile tires, which contain reinforced embedments of textile or other substances, such as wire mesh or the like.
Specifically, the invention relates to a method of carrying out such fragmenting, and to an apparatus for carrying out the method.
It has long been the general practice to discard automobile tires and analogous articles made of rubber or synthetic plastic material which have become worn and unuseable. The general practice has been to either bury such articles or to burn them. In recent years, however, it has been recognized that it is unwise economically and ecologically to discard so large a source of potentially recoverable materials, especially in an age of dwindling supplies of raw materials. It has therefore been proposed in the prior art to provide equipment for recovering the rubber or synthetic plastic material of automobile tires or analogous articles which have become otherwise unuseable. Particularly in the case of automobile tires, this essentially presents the problem of separating the rubber or synthetic plastic of the tire from the textile or metallic reinforcements which are embedded in the tire.
The prior art has proposed to freeze the articles to be processed, based on the well known fact that rubber and synthetic plastic material become brittle when frozen and can therefore be more readily fragmented. Thus, one prior-art proposal suggests to freeze the tires, place them flat upon an anvil plate and pound them with a mechanically or hydraulically actuated hammer or ram which is intended to fragment the tire.
Unfortunately, the prior-art approach has not been entirely satisfactory, because a satisfactory separation of the rubber or synthetic plastic material from the embedded reinforcements could not be obtained. Even if the blows upon the tire, which term hereafter will be used generically to refer to all articles whose rubber or synthetic plastic material is to be recovered, are repeated several times, the results are not satisfactory because the hammer hits the tire always in the same places. Especially the rather strong and resistant wire rings which are embedded in the bead of the tire are hit always transverse to their general plane, so that they are not subjected to any bending stresses and do not become satisfactorily separated from the tire material. When subsequently the more or less fragmented tire is passed though a magnetic separator to remove any wire or metallic components from it, these metallic components always take along a rather large proportion of the rubber or synthetic plastic material which still adheres to them and has not been satisfactorily separated from them, and this proportion is either lost or must be removed by a separate and expensive operation. If textile reinforcements are involved which also cannot be satisfactorily removed according to the prior art, then they continue with the more or less fragmented tire material into a subsequent comminuting mill in which they are comminuted together with the rubber or synthetic plastic tire material and contaminate this material.